Rotary tool



March 21, 1939. E, E, HINDMN 2,151,274

` ROTARY TQoL Filed Jan. l5, 1936 Earl Edward Findman,

Patented Mar. 21, 1939 UNITED STATES PATENT OFFICE Claims.

manufactured and sold at a low cost and which v will have novel features and improved utility.

A further object is to provide a novel combined switch control, manual speed control, and automatic brake.

Additional objects, advantages and features of invention reside in the construction, arrangement and the combination of parts involved in the embodiment of the invention, as will appear from the following description and accompanying drawing, wherein Figure 1 is a longitudinal sectional view of one embodiment of the invention;

Figure 2 is a top view thereofl with parts broken away;

Figure 3 is a cross section on the line 3--3 of Figure 2.

Figure 4 is a section on the line 4-4 of Figure l.

Figure 5 is a longitudinal sectional view of a preferred embodiment of the invention.

Figure 6 is a cross section thereof on the line Figure 7 is a left end view of the case.

There is illustrated in Figs. 5 and 6 an electric eraser comprising a case I0, formed of a central cylinder I I on which frontend back case cap sections vlz and la' are ntted and secured in any approved manner. Centrally of the back section I2 a bushed opening I4v is formed through which wires I5-I5' are led to a motor and switch to be described, and there are also formed 4 en inlet holesv ls. A cross need n 1e me@ in tnecase section I3 constructed to permit passage of air thereby, and formed on the front side with a ball race in which ball bearings I3 are held by a cone I9 xed on the main Vshaft 2li.

The' forward end of the shaft is projected freely through the case head II, in which there is screwed for adjustability a race 2l, in which ball bearings 22'are provided supporting a cone 23 fixed on the shaft. Around the race 2l a series of tapered air jet `openings 24 are formed in the head II having their axes inclined toward a point on the axis of the shaft a distance outwardly of the case, for purposes to be described.

36 Within the head I2 a fan 25 is mounted on the ings 28 mounted on the cylinder II.

(ci. 11a-ssi The invention has for an object to present an shaft 20 adapted to propel air throughthe aperture 24. y

A motor 26 is conventionally shown, which may be of any suitable type, including the armature 21 mounted on the shaft 23, and field wind- 5 Commutator rings 23 are shown although other commutator forms may be used as required. Brushes 30 are mounted on the cross head Ii, and suitable terminals provided for each, to one of which the 1o wire I5 is led, the wire Ii' being extended through the motor directly to a switch 3| mounted on the case section I I forwardly beyond the motor. The switch comprises a plate 32 fixed on. the case and projected transversely of the case near the 15 shaft 20, having an vinsulated contact 33 thereon to which the wire I5' is connected. Mounted in the same transverse plane of the case at the opposite side, there is an insulated spring switch arm 34 curved concentrically with the case to lie 20 parallel to the case wall, and extended over the contact 33, between the latter and the wall of the case. The arm 34 hasa lateral extension 35, which projects longitudinally of the case toward the forward end, its extremity offset toward the 25 shaft 26 so as to lie under a brake shoe 36, carried on a plunger 31 mounted radially in the forward end of the case, and having a nger piece 33 at its outer end confining a helical spring 33 against a bushing 40, fixed in the case 30 and serving as the mounting for the brake.

When the brake shoe is in retracted position, the extension 35 rests against the shoe, and the switch is open. A contact 4I is mounted on the arm 34 to engage the contact 33 when the switch 35 arm is depressed, and from the contact 4I a lead 42 is extended to the eld coils 26.

0n the shaft 20 alined with the brake shoe 36, there is a brake wheel or collar 43 upon which the shoe may engage after the switch is closed, 40 by continued movement of the plunger. 'I'he extension 35 of the switch arm stops short of the wheel, so as not to contact therewith or interfere with yapplication of the braigel' The extension is strong enough to cause the arm 34 to be bent downward to close the switch on initial depression of the plunger before the shoe 36 engages the whee143, and afterclosure of the switch if the plunger is pressed farther, further movement of the brakey shoe is permitted by fiexure of the extension 35 or by torsion of the `arm 34. The wires I5-I5' may be provided with any usual electrical tting at their outer ends, such as a plug of approved form whereby the appliance may be connected to standard outlets in oflices, studios, shops, and elsewhere.

On the extreme forward end of the shaft 20. without the case, a tool is provided, shown in the present instance as an eraser device consisting of a metal holder 44 of cylindrical form iixed on the shaft by means of a pin 44', being open at its outer end, and having inserted slldably and removably therein a solid cylinder eraser proper 45 which may be made of any materials usual in erasers, suited to the character of work upon which the device is to be used. In this instance, the eraser is also adjustable in the holder to compensate for wear. For this purpose the holder 44 is formed with a spiral slot 46 of suitable pitch, and in the side o! this slot next the base of the holder there are formed extensions 41 or notches 41 extended longitudinally of the axis o! the holder. 'I'he slot is open at its outer end on the extremity of the holder, and the notches may be provided at close intervals along the slot it desired. In the base of the eraser 45 there is Iixed a lateral pin 48 movable freely along the slot and adapted to be adjusted in any of the notches 41. 'Ihe eraser 45 is also shown in Figure 5 as having a spiral groove 5|! therein on its periphery and preferably extending from near the base of the eraser in the direction of rotation of the holder and opening on the outer end of the eraser. The groove may be longitudinal and be comparatively shallow, so as to not weaken the eraser excessively or cause liability oi. its breakage or excessive flexibility. Y

The direction of rotation of the holder is prei'- erably opposite to the outward direction'of the spiral slot in the holder 44, whereby the tendency of the eraser to become too deeply -set in the holder it loosened is minimized.

In the use of the form of the device described, the holder 44 having an eraser adjusted therein and the lead wires being connected to a suitable electrical source, the appliance is grasped in the hand after the manner of a pencil, and the lpoint of the eraser applied t5 the matter to be erased while the forenger or thumb is pressed upon the inger-piece. In case a slight abrasive action is desired, the finger-piece may be pressed down hard enough to apply the brake as required, and thus slow the rotation ot the motor and avoid excessive wear of the surface of the work. The fan 25 will propel jets of air upon the surface ot the work, and remove the particles of abraded ,material and eraser.l Also at the same time the groeve in the eraser will gather particles that tend to form under the eraser and throw them away from the point of application of the eraser. drawing them backwardly from the point oi' the eraser so that the point of application on the work does not become obscured. and the air jets remove these particles to a distance so that the 'erased area is cleared .and the condition of the work is apparent at all times.

When the eraser becomes worn down too close to the holder, the motor is stopped and the outer end of the eraser grasped in the lingers of one hand and drawn outward with a twisting motion in the direction cf the turn of the s lot 46. When projected sufliciently from the lholder the eraser is then thrust longitudinally inward without applying any twisting force manually. This causes the pin 48 to bear against and slide upon the side of the slot having the notches 41 in it, ro tating the eraser slightly relatively to the holder, and when the first notch 41 is encountered, the pin 48 will enter the same and stop further entry the magnet, the

or relative rotation of the eraser in the holder. When the eraser is applied to the Work while being rotated, the pressure of the work thrusts the pin 48 into the notch securely, and assures maintenance o! the eraser in the adjusted position.

By having the motor turn in a direction opposite the outward direction of the spiral slot, ii.' the device should be vibrated or jarred during use, or the pin 4B dislodged from one of the notches 41 momentarily, the eraser would tend to retain its position by the pressure of the in clined side of the slot against the pin 48, Whereas, if the device rotated in the opposite direction, the eraser might be drawn further into the holder, and possibly the holder allowed to engage the surface of the work. Also, in case of such engagement rotation counter to the direction of the slot would minimize liability of gouging the work by the advancing angularity at the outer side of the slot.

The eraser may be formed with a longitudinal groove 49, as in the eraser 45 of Figure 5 or a number of such grooves provided, or the eraser may be made without any groove, as at 45a in Figure 1.

In Figures 1 to 4 a varied construction of the motor is illustrated, which may be employed if desired. In this instance, the shaft 20' is mounted at its forward end substantially as in Figure 5, but the bearing for its rear end is located midway of the case IU' which is conventionally shown in one piece, instead of at the rearmost part. This bearing is in a block 5|, and is similar to that in the cross head I1. The block 5| is slotted at one side to receive for oscillation therein one arm 52 of a bell crank lever 53, plv-J oted between two ears 54 formed on the outer side of the block 5|. The other arm extends inward transversely of the case and carries an armature 55 in operative relation to an electro-magnet 56 mounted in the outer part of the case.

The arm 52 of the lever is branched and its furcations inclined inwardly so as to terminate on a diametrical line of the shaft 2D a ratchet wheel 51 being mounted on the shaft between the extremities of the furcations, and spring pawls 58 being mounted in the ends of the furcations inclined in opposite directions, so that the wheel will be propelled by each movement of the bell crank in each direction. The bell crank is held yieldingly at one limit of its movement by means o1' a spring 59. A switch 60 is provided which may be the same as that first described, although the switch arm is shown as a simple leaf spring 6i extending longitudinally of the case, one end being fixed to the case and the otherv attached to the plunger 31', the latter being similar to the one 31 and having similar use in operating the switch and a brake 62, which engages the shaft 20 after substantial depression of the spring. The switch is located intermediately of the spring, which carries a contact 63 connected to one of the lead-in wires, and engages a stationary contact 64 from which a wire 65 leads to other lead-in Wire being connected directly to the magnet. The use of this device is similar to that-first described, except -that no fan is shown and no air jetused. The

Ain

to be erased in typewriting, the eraser is positioned with its axis crossing the line, and the point only laid over the letter to be erased. The same may be done on drawings, and like principles of application followed in correcting drawings, generally.

Various eraser forms, tool heads and implements may be used interchangeably on the appliance, either using the holder 44 or other mounting means.

The case I may also have an air aperture or more therethrough as at 66, and any suitable source of compressed air may beV connected to the inlet opening I6' to supply air to the eraser for clearing the detritus.

In some aspects of the invention as hereinafter claimed, other motor devices may be utilized than those described, electric or otherwise.

Means may be provided in the device to cut off or diminish the amount of air discharged through the openings of the cases, and in Figures and 6, this is shown as a cap 61 revolubly fitted over the cap I2 and having two imperiorate areas adapted to lie over the openings 24 at one position, and graduated pairs of apertures B8 adapted to be brought successively into alinement with the apertures 24 by rotation of the cap 61 on the case. The inner edge of the cap 61 has inturned retaining tongues 69 engaging the inner edge of the cap I2. As seen in Figures 5 and 6, the brake shoe 36 is provided with an extension 36a extending downwardly and inwardly beneath the wheel 43, and so positioned that on release of the plunger rising of the latter will lift the lower part of the shoe against the under side of the wheel, acting as a stop motion for the shaft as well as a stop for the plunger.

I claim:

1. In a hand tool which comprises a hand case, an axial revoluble tool-carrying shaft mounted therein, a motor operatively connected with the shaft, meansv to control the motor: a combined control operating means and brake including a finger-operated plunger, brake means on the plunger in operative relation to the shaft, a yielding member operatively connected with the plunger and the control, said brake being in lost motion relation to the shaft, whereby the brake will engage by continued movement of lthe plunger after beginning of operation of the motor, and means to retract the brake.

2. In a rotary hand tool which comprises a case, a motor mounted therein` having a motor shaft revoluble in the case, a tool mounting thereon exteriorly of the case, electrical connections for the motor and a switch: a combined switch operating and brake device consisting of a movable switch arm, a spring pressed plunger in the case operatively connected with said arm to normally hold the switch open and having a finger piece exposed whereby to be engaged by the finger and depressed to operate the switch, the connection between the switch and plunger including a resilient element yieldable to further depressive movement of the plunger after closing of the switch and ay brake device operatively associated with the shaft, including a brake shoe having spaced relation to the shaft when the switch is initially closed, and movable with the plunger thereafter to engage a friction part on 'the shaft.

second element thereon positioned to engage the shaft opposite the first named brake at initial position of the plunger, and the rst named brake operates to control the speed of the shaft while in motion.

4. In a combined switch and speed control for motors of the character described, a motor having a shaft and a case, a friction member on the shaft, a switch comprising a case-carried contact, a movable case-carried switch arm having a contact positioned to engage the rst contact and tending to move therefrom, said arm having a resilient yieldable part extended beyond the contact a material distance, a finger piece engaged therewith for movement of the arm to closed circuit position and beyond, and a brake member positively connected with the finger piece and initially spaced from the friction member more than the distance which it moves from initial position to closed switch position.

5. The structure of claim 4 in which said brake member has an extension beyond the friction 

